Vitamin D Blog: Cancer Risk in IBD

In this Guest Blog, Ashwin N. Ananthakrishnan, MBBS, MPH, a gastroenterologist at Massachusetts General Hospital in Boston, discusses his recent study on vitamin D and its relationship with cancer in patients with inflammatory bowel disease.

Vitamin D has pleiotropic effects on the immune system and has been associated with reduced risk of autoimmunity, cardiovascular disease, and cancer. Yet there are no data on the association between vitamin D and cancer in chronic immune-mediated diseases where mechanisms of cancer may be distinct and other competing factors may influence both vitamin D status and cancer risk.

My team at Massachusetts General Hospital in Boston is interested in uncovering the connection between vitamin D and inflammatory bowel disease (IBD). Although a third of IBD patients are vitamin D deficient and an equal proportion have insufficient levels, there has been only limited study of potential longitudinal consequences.

Cross-sectional studies suggested an association between vitamin D status and disease activity, a finding that was confirmed in a study from our group demonstrating an inverse association with IBD-related hospitalizations and surgery. We have also shown that normalization of vitamin D levels is associated with a reduction in the risk of IBD-related surgery.

Since no prior studies have examined the effect of vitamin D status on the risk of cancers in patients with IBD, we looked into the issue using a well-characterized, multi-institutional IBD cohort involving 2,809 patients. We assessed several types of cancers to see if the effect of vitamin D is specific to certain cancer subtypes in the IBD population.

We found that low vitamin D is associated with an increased risk of metastatic and nonmetastatic cancers -- and the association was strongest for colorectal cancer.

There were, of course, limitations. Our cohort is based primarily at two referral centers, so the population may be skewed toward greater severity of underlying IBD. Also, we did not have information on body mass index or smoking status, both of which have been associated with overall risk of malignancy and colorectal cancer -- although the effect of BMI and smoking on IBD-related cancers has not been noted previously.

Nor did we have information on medications such as aspirin and nonsteroidal anti-inflammatory drugs, both of which have been inversely associated with the development of colorectal cancer. However, long-term use of such medications is uncommon in patients with IBD because of their potential to trigger disease relapses.

Nevertheless, to our knowledge, this remains the largest cohort containing information on the vitamin D status of patients with IBD. Based on our findings, an assessment of vitamin D status should routinely be part of comprehensive care of patients with IBD.

I know from treating patients with IBD that controlling symptoms can be a daily struggle. Luckily, vitamin D is relatively easy to monitor and maintain and may offer long-term health benefits for those with the disease. However, we need much more rigorous data to examine the role of vitamin D, safety with various doses of supplementation, and clinical trials examining its effect on disease activity and other outcomes in patients with IBD.

Have a tip on a vitamin D study? Email Kristina Fiore at k.fiore@medpagetoday.com. You can also catch our vitamin D feed on Twitter, @vitaminDblog.

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